Growing environmental demands and the need for higher efficiency vehicles—dictated to a great extent by concerns relating to global warming—has triggered great interest in fuel cells as propulsion systems for transportation vehicles. This has prompted an extensive search for new methods of delivering hydrogen fuel to these cells. One of the most likely options for delivering hydrogen fuel is to provide on-board reforming of liquid hydrocarbon fuels coupled with hydrogen separation.
Gasoline has evolved over many decades to satisfy the requirements of the internal combustion engine. As the prospect of vehicles employing fuel cells moves closer to being a reality, petroleum companies must consider how fuel specifications will change. For example, “octane” as used for gasoline is a useless performance index for a fuel cell power platform and, in fact, typical octane enhancers actually complicate the process.
Several fuels have been suggested as possible candidates for fuelling fuel cell vehicles. These include methanol, F-T naphtha and diesel, and hydrogen. With the development of fuel reformers capable of converting liquid hydrocarbon fuels into hydrogen, the likelihood of using a purely hydrocarbon fuel becomes more feasible. While several fuels have been suggested, and a few have been tested, the concept of optimizing and designing a naphtha-based fuel is both intriguing and reasonable, since it has a low degree of volatility, a high hydrogen content, ready availability and low cost.
This option also provides a safe fuel which is compatible with existing service stations, supply, distribution, and storage infrastructure, as well as the most economic system of fueling. Low-volatility liquid hydrocarbon fuels may be stored in existing vehicular and service station tanks, pumped with existing equipment, and transported through existing pipelines and by truck, marine and rail tankers.
A method for producing raw materials for a reformer by cracking and desulfurizing petroleum fuels is disclosed in U.S. Pat. No. 5,284,717 to Yamasee and which is incorporated herein by reference. This patent discloses an integrated system for stationary fuel cell electric power generation from diesel or naphtha. The fuel treatment process relies on a single stage zeolite or silicate-supported catalyst typically of the cobalt, molybdenum, nickel, iron, tungsten, chromium or gallium type. In the disclosed process, the feedstocks are cracked, or reduced in molecular weight, the aromatic content is increased, and a large proportion of the liquid fuel is converted to gas. The combined fuel crackate is treated in an adsorber to remove hydrogen sulfide, then fed directly to a steam reformer to produce a syn-gas mixture. However, there is no disclosure of hydrogenerating aromatics, or producing a naphtha range liquid, which is isolated, stored, then provided for fueling ground-based transportation vehicles. Also, there is no suggestion of providing a process which reduces aromatics, increases hydrogen content, and which results in a low RVP liquid fuel which is sulfur-free and suitable for automobiles.
It is, accordingly, an object of the present invention to provide a naphtha-based fuel for use in a fuel cell and/or a fuel cell reformer.
It is another object of the present invention to provide a naphtha-based fuel which has an extremely low sulfur content, as well as a high hydrogen content and a low aromatics content to provide an efficient and compatible fuel for a fuel cell and/or fuel cell reformer.
It is a further object of the present invention to provide a process for producing a naphtha-based fuel which is efficient and compatible with a fuel cell and fuel cell reformer, which fuel has an extremely low sulfur content, a high hydrogen content and a low aromatics content.